A Stability Assessment Methodology

Weak transmission boundaries are shown to cause steady state and transient stability problems. The weak boundaries are defined by a loss of controllability property of the transient stability model. The loss of synchronism for fault contingencies can occur across these weak boundaries [7] if this boundary is weak compared to the other cutsets that encircle but are closer to the fault location. A loss of transient or steady state stability due to loss of generation contingencies will also occur across the elements in these weak boundaries. The inadvertant flows for inertial and governor response to loss of generation contingencies focus back to the region experiencing the loss of generation. These inadvertant flows cross the weak transmission boundaries and are shown to cause loss of generation and the formation of islands across the cutset of transmission elements that constitute the weak transmission boundaries. A method for determining and ranking the weak transmission boundaries of the transient stability model is developed. A method of determining and ranking the vulnerability of transmission elements is also determined. The measures used to determine the weak boundaries and vulnerable transmission elements for loss of generation or fault contingencies can be determined by summing the angle changes for all inertial load flow simulated loss of generation contingencies. The measures and the method for determining the weak transmission boundaries can be proven to detect the loss of controllability property of the transient stability model that define the weak boundaries.